API with Multiple GET Parameters in PHP

Now let's assume that not one parameter, but several will be passed. For example, two numbers:

urlhttp://api.loc/index.php?num1=1&num2=100

Let's return a random number in the range from the first passed number to the second one:

api.loc/index.php<?php
  if (isset($_GET['num1']) and isset($_GET['num2'])) {
    echo mt_rand($_GET['num1'], $_GET['num2']);
  } else {
    echo 'error';
  }
?>

Задание 1

Create an API with an address, to which two parameters will be passed: dates in the format year-month-day, and in response the number of days between these dates will be returned.

Задание 2

Modify the previous task so that a check for the correct date format is performed.